Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$118.90	10.711%	$131.6354	$131.64	$131.65	$131.60
Purchase #2	$91.62	11.328%	$101.9987	$102.00	$102.00	$102.00
Purchase #3	$104.29	4.532%	$109.0164	$109.02	$109.00	$109.00
Purchase #4	$84.84	6.666%	$90.4954	$90.50	$90.50	$90.50
Purchase #5	$129.55	7.338%	$139.0564	$139.06	$139.05	$139.10
Purchase #6	$27.84	12.820%	$31.4091	$31.41	$31.40	$31.40
Purchase #7	$118.68	7.830%	$127.9726	$127.97	$127.95	$128.00
7 purchase totals =	$675.72		$731.5840	$731.60	$731.55	$731.60